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Tuesday, April 3, 2012

Piezo Buzzer Driver Circuit Diagram

Buzzers are small, light, simple to use, and yet provide a loud
output signal. They are either of the passive or of the active type.

The former are driven by an AF signal source, while the latter
feature a built-in oscillator, and require a direct voltage only. This
circuit is a double AF oscillator for driving passive buzzers. It
ensures a richer out- put sound than normally obtain- able from a piezo
buzzer due to the use of two oscillators, N1 and N2, whose output signal
lies between 1 and 10 kHz. Gates Na-N4 form an S-R bistable which is
controlled by the out- puts of N1-N2, and drives the buzzer direct.

Optimum effects are achieved when a simple ratio is set between the oscillator frequencies, e.g. 3:4.

Piezoelectric resonators, also referred to as buzzers, are
frequently used for providing audible signals in all sorts of electronic
equipment.

The spectral l composition of the output X signal is fairly complex,
due to the presence of both the fun- damental notes and the differ-
ence and sum frequency.

The timbre so obtained varies as a function of the ratio between the
oscillator frequencies, which are adjustable with the aid of presets
P1-P2. Note that diodes D1-D2 reduce the duty factor of the oscillator
signals to about 25%.

The resulting waveform is always composed of rectangular signals,
but these differ in respect of their period to ensure that the buzzer
pro- duces a rather agreeable sound. The buzzer driver is controlled by a
logic level applied to point X. The quiescent current consumption is
virtually negligible, while about 10 mA is drawn in the actuated state.